The vexed question of how easy it will ever be to wean markets away from stimulus has been forced on us all again. It was back in May that Monument Securities’ chief economist Stephen Lewis called stimulus a tiger from which Mr. Bernanke “dare not dismount”. Four months on we can still see the teeth and the stripes.

Of course, matters haven’t been helped by the ominous approach of budget and debt ceiling battles in Washington. When faced with this particular beast, global investors tend to hope they can ignore it, secure in the knowledge that the U.S. will find a last minute deal to slay it before the Federal government gets toasted. And that’s always what happens. But even so markets are twitchy in the run-up, and are likely to be more so now that we know even the U.S. top credit ratings aren’t immortal.